Tumor suppressor gene

ABSTRACT

A full-length cDNA encoding novel proteins involved in the control of cell proliferation (human Gros1-L and S) was successfully isolated from the human testis cDNA libraries. A full-length cDNA encoding the mouse homologues of the human Gros1 (mouse Gros1-L and S) was also isolated. The colony forming activity of cells exogenously expressing Gros1-L was significantly reduced, while that of cells expressing Gros1 antisense RNA was significantly increased.

This application is a divisional of application Ser. No. 12/626,290, filed on Nov. 25, 2009, issued as U.S. Pat. No. 7,825,220 which is a divisional of application Ser. No. 11/603,619, filed Nov. 22, 2006, issued as U.S. Pat. No. 7,642,070 which is a divisional of application Ser. No. 10/045,815, filed Oct. 26, 2001, issued as U.S. Pat. No. 7,153,935, which is a continuation-in-part of PCT Application Serial No. PCT/JP00/02731, filed Apr. 26, 2000, and claims priority to Japanese Patent Application No. 11-118806, filed Apr. 26, 1999. The disclosure of these prior applications is incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to the field of biological science, more specifically to the field of cancer research. In particular, the present invention relates to novel proteins involved in the proliferation mechanism of cells. The proteins of the present invention can be used, for example, as target molecules for developing drugs against cancer.

BACKGROUND

From a cytogenetic and molecular biology perspective, there appears to be a non-random mutation on human chromosome 1p in many malignant tumors (Caron, Med. Pediatr. Oncol., 24:215-221, 1995; Schwab et al., Genes Chromosomes Cancer, 16:211-229, 1996). For example, deletions in the region of chromosome 1p have been found in various oncocytes (neuroblastomas [White et al., Eur. J. Cancer, 33:1957-1961, 1997, Gros16; Ariyama et al., Genomics, 25:114-123, 1995; Cheng et al., Oncogene, 10:291-297, 1995], meningiomas [Ishino, et al., Cancer, 83:360-366, 1998], pheochromocytomas, medullary thyroid carcinomas, neuroendocrine tumors [Moley et al., Cancer Res., 52:770-774, 1992], T cell acute lymphoblastic leukemia (T-ALL) [Iolascon et al., Leukemia, 11:359-363, 1997], colorectal cancers [Praml et al., Oncogene, 11:1357-1362, 1995, Gros13; Bomme et al., Genes Chromosomes Cancer, 21:185-194, 1998; Di Vinci et al., Cancer, 83: 415-422, 1998], mesotheliomas [Lee et al., Cancer Res., 56: 4297-4301, 1996], hepatomas [Chen et al., Cancer Genet Cytogenet, 86:102-106, 1996], endometrial carcinomas [Arlt et al., Hum. Mol. Genet, 5:1017-1021, 1996], and breast cancers [Nagai et al., Cancer Res., 55:1752-1757, 1995; Munn et al., Oncogene, 10:1653-1657, 1995]. etc.). In addition, mutations in the 1p region are thought to correlate with lymph node metastasis and tumor size [Borg et al., Genes Chromosomes Cancer, 5:311-320, 1992; Tsukamoto et al., Cancer, 82:317-322, 1998]. Moreover, the genetic mutation associated with endodermal sinus tumors (CESTs) developed in small children under four years is proposed to occur on chromosome 1p [Perlman et al., Genes Chromosomes Cancer, 16:15-20, 1996]. These facts indicate that one or more genetic mutations in chromosome 1p are associated with malignant tumors. However, the causative gene has not yet been discovered.

SUMMARY

The object of the present invention is to provide a novel protein involved in the proliferation mechanism of the cells and the gene encoding the protein, as well as methods for producing and using the same.

The present inventors screened the mouse RS-4 cell cDNA library according to the immunoscreening method using antibodies against protein p33, which is about 30 kDa in size and contained in the Triton X-100 insoluble fraction of the immortalized cell (NIH3T3) plasma membrane P100 fraction. Using thus obtained cDNA as a probe, human testis library was screened and the inventors succeeded in cloning the novel gene, Gros1, from the library. Two types of human Gros1 cDNAs (SEQ ID NOs:1 and 3) exist: one encodes a protein consisting of 363 amino acids (designated “human Gros1-S protein”, SEQ ID NO:2), and the other encodes a protein consisting of 736 amino acids (designated “human Gros1-L protein”, SEQ ID NO:4).

Moreover, using the cDNAs obtained by the above immunoscreening method as a probe, mouse testis library was both screened and searched for ESTs, to successfully identify mouse Gros1-L cDNA (SEQ ID NO:5) and mouse Gros1-S cDNA (SEQ ID NO:7). They encode a protein consisting of 747 amino acids (SEQ ID NO:6) and 542 amino acids (SEQ ID NO:8), respectively.

Human and mouse Gros1s were found to be homologous to the novel basement membrane-associated proteoglycan found in the data bank, leprecan, isolated from rat cDNA (Wassenhove-McCarthy et al., J. Biol. Chem., 274:25004-25017, 1999). In addition, as a result of the motif search analysis of amino acid sequences, the amino acid sequences of mouse and human Gros1-Ls were found to comprise the leucine zipper structure often observed in some members of the transcription factors.

As the result of chromosome mapping of human Gros1, the Gros1 gene was found to exist on the human chromosome 1 short arm (1p), a site suggested to have non-random mutations in many malignant tumors (Caron, Med. Pediatr. Oncol., 24:215-221, 1995; Schwab et al., Genes Chromosomes Cancer, 16:211-229, 1996).

The amount of Gros1 mRNA expressed in tissues, cells and those during developmental stages was detected by Northern blot analysis. As a result, in human, 4.4 kb and 2.5 kb bands were strongly expressed in testis, ovary and placenta, and weakly in most other tissues (FIG. 4). In addition, mRNA expression was higher in cultured human cells than in above tissues, and, in human normal cultured cells, the expression of the 2.5 kb mRNA was almost 10 times higher than that for the 4.4 kb mRNA (FIG. 5). In mouse, 3.5 kb and 2.5 kb bands were weakly expressed in most tissues, not expressed in brain or spleen; only the 2.5 kb band was expressed in the testis. Accordingly, in the testis and ovary, only the shorter form among the two transcripts of the Gros1 genes was detected. The expression during the developmental process was shown to dramatically disappear on the 11th day of the developmental process (FIG. 6).

The present inventors performed a function analysis of Gros1 by introducing the gene encoding the mouse 85 kDa protein (Gros1-L; SEQ ID NO:6) into NIH3T3 cells. As a result, cell proliferation was repressed and colony forming activity was decreased in cells expressing the full-length Gros1-L as compared to those of the control and Gros1 whose C-terminus is deleted. On the other hand, in cells in which antisense RNA of Gros1-L was expressed, the colony forming activity increased 5 folds.

Based on these analyses, Gros1 proteins are thought to be novel genes involved in the control of cell proliferation, and related to the development and growth of tumors. Thus, Gros1 proteins are useful as tools for developing pharmaceuticals against tumors.

The present invention relates to novel proteins (Gros1) involved in cell proliferation and the genes encoding them, as well as the production and the use the same. More specifically, the present invention provides the following:

1. A DNA of any one of the following (a) to (d):

-   -   (a) a DNA encoding the protein consisting of the amino acid         sequence of any one of SEQ ID NOs:2, 4, 6, or 8;     -   (b) a DNA containing the coding region of the nucleotide         sequence of any one of SEQ ID NOs:1, 3, 5, or 7;     -   (c) a DNA encoding a protein consisting of the amino acid         sequence of any one of SEQ ID NOs:2, 4, 6, or 8, in which one or         more amino acids are replaced, deleted, inserted, and/or added,         the encoded protein being functionally equivalent to the protein         consisting of the amino acid sequence of any one of SEQ ID         NOs:2, 4, 6, or 8; and     -   (d) a DNA hybridizing under stringent conditions with a DNA         consisting of the nucleotide sequence of any one of SEQ ID         NOs:1, 3, 5, or 7, and encoding a protein functionally         equivalent to the protein consisting of the amino acid sequence         of any one of SEQ ID NOs:2, 4, 6, or 8.

2. A DNA encoding a partial peptide of the protein consisting of the amino acid sequence of any one of SEQ ID NOs:2, 4, 6, or 8.

3. A vector into which the DNA of (1) or (2) is inserted.

4. A transformed cell harboring the DNA of (1) or (2), or the vector of (3).

5. A protein or peptide encoded by the DNA of (1) or (2).

6. A method for producing the protein or peptide of (5), comprising the steps of culturing the transformed cell of (4), and collecting the protein expressed from the cells or the culture supernatant thereof.

7. An antibody binding to the protein of (5).

8. A polynucleotide hybridizing with the DNA consisting of the nucleotide sequence of any one of SEQ ID NOs:1, 3, 5, or 7 or the complementary strand thereof, and comprising at least 15 nucleotides.

9. A method of screening for a compound that binds to the protein of (5), comprising the steps of

-   -   (a) contacting a subject sample with the protein or the partial         peptide thereof;     -   (b) detecting the binding activity of the subject sample with         the protein or the partial peptide thereof; and     -   (c) selecting the test compound that binds to the protein or the         partial peptide thereof.

10. A compound binding to the protein of (5), which can be isolated by the method of (9).

11. A method of screening for a compound that promotes or inhibits the activity of the protein of (5), comprising the steps of:

-   -   (a) culturing cells which express the protein or the partial         peptide thereof in the presence of a subject sample;     -   (b) detecting the proliferation of the cell; and     -   (c) selecting the compound that promotes or inhibits the         proliferation as compared to the proliferation detected in the         absence of the subject sample.

12. A compound that promotes or inhibits the activity of the protein of (5), which can be isolated by the method of (11).

The present invention provides a novel protein Gros1 involved in the cell proliferation mechanism. SEQ ID NOs:1 and 3 show nucleotide sequences of the cDNA of two types of human Gros1 (human Gros1-S and human Gros1-L, respectively) isolated by the inventors, and SEQ ID NOs:2 and 4 show the amino acids sequences encoded by the cDNAs, respectively. SEQ ID NOs:5 and 7 show nucleotide sequences of the cDNA of two types of mouse Gros1 (mouse Gros1-L and mouse Gros1-S, respectively) isolated by the present inventors, and SEQ ID NOs:6 and 8 show the amino acids sequences encoded by the cDNAs, respectively.

When the Gros1-L protein was expressed exogenously in NIH-3T3 cells, cell proliferation was inhibited and the colony forming activity decreased. In contrast, when the expression of Gros1-L protein was repressed by the introduction of Gros1 antisense cDNA in NIH-3T3 cells, the colony forming activity increased dramatically. Thus, the Gros1 protein is considered to be involved in the control of cell proliferation. This is also supported by the fact that human Gros1 gene is present on chromosome 1 short arm (1p), a site that is purportedly associated with malignant tumors. Therefore, the Gros1 proteins of the present invention can be conveniently used as tools, for purifying or cloning factors controlling cell proliferation, as well as targets, for example, for screening candidate compounds of drugs useful for treating or preventing disorders related to cell proliferation, such as tumors. Moreover, the Gros1 genes can be applied in the treatment, for example, gene therapy for various tumors.

The present invention encompasses proteins functionally equivalent to the Gros1 proteins. Such proteins include, for example, homologous proteins of other organisms corresponding to the human or mouse Gros1 protein, as well as mutants of human or mouse Gros1 proteins.

In the present invention, the term “functionally equivalent” means that the subject protein has the activity to inhibit cell proliferation like Gros1 proteins. Whether the subject protein has a cell proliferation inhibitory activity or not can be judged by introducing the DNA encoding the subject protein into a cell, such as NIH-3T3, expressing the protein, and detecting repression of proliferation of the cells or reduction in colony forming activity.

Methods for preparing proteins functionally equivalent to a given protein are well known by a person skilled in the art and include known methods of introducing mutations into the protein. For example, one skilled in the art can prepare proteins functionally equivalent to the human or mouse Gros1 protein by introducing an appropriate mutation in the amino acid sequence of the human or mouse Gros1 protein by site-directed mutagenesis (Hashimoto-Gotoh et al., Gene, 152:271-275, 1995; Zoller et al., Methods Enzymol., 100:468-500, 1983; Kramer et al., Nucleic Acids Res., 12:9441-9456, 1984; Kramer et al., Methods Enzymol., 154:350-367, 1987; Kunkel, Proc. Natl. Acad. Sci. USA, 82:488-492, 1985; Kunkel, Methods Enzymol., 85:2763-2766, 1988). Amino acid mutations can occur in nature, too. The protein of the present invention includes those proteins having the amino acid sequences of the human or mouse Gros1 protein in which one or more amino acids are mutated, provided the resulting mutated proteins are functionally equivalent to the human or mouse Gros1 protein. The number of amino acids to be mutated in such a mutant is generally 10 amino acids or less, preferably 6 amino acids or less, and more preferably 3 amino acids or less.

Mutated or modified proteins, proteins having amino acid sequences modified by deleting, adding and/or replacing one or more amino acid residues of a certain amino acid sequence, have been known to retain the original biological activity (Mark et al., Proc. Natl. Acad. Sci. USA, 81:5662-5666, 1984; Zoller et al., Nucleic Acids Res., 10:6487-6500, 1982; Wang et al., Science, 224:1431-1433; Dalbadie-McFarland et al., Proc. Natl. Acad. Sci. USA, 79:6409-6413, 1982).

The amino acid residue to be mutated is preferably mutated into a different amino acid in which the properties of the amino acid side-chain are conserved. Examples of properties of amino acid side chains are hydrophobic amino acids (A, I, L, M, F, P, W, Y, V), hydrophilic amino acids (R, D, N, C, E, Q, G, H, K, S, T), and side chains having the following functional groups or characteristics in common: an aliphatic side-chain (G, A, V, L, I, P); a hydroxyl group containing side-chain (S, T, Y); a sulfur atom containing side-chain (C, M); a carboxylic acid and amide containing side-chain (D, N, E, Q); a base containing side-chain (R, K, H); and an aromatic containing side-chain (H, F, Y, W). (The parenthetic letters indicate the one-letter codes of amino acids).

An example of a protein to which one or more amino acids residues are added to the amino acid sequence of human or mouse Gros1 protein (SEQ ID NOs:2, 4, 6, or 8) is a fusion protein containing the human or mouse Gros1 protein. Fusion proteins are, fusions of the human or mouse Gros1 protein and other peptides or proteins, and are included in the present invention. Fusion proteins can be made by techniques well known to a person skilled in the art, such as by linking the DNA encoding the human or mouse Gros1 protein of the invention with DNA encoding other peptides or proteins, so that the frames match, inserting the fusion DNA into an expression vector and expressing it in a host. There is no restriction as to the peptides or proteins fused to the protein of the present invention.

Known peptides that can be used as peptides that are fused to the protein of the present invention include, for example, FLAG (Hopp et al., Biotechnology, 6:1204-1210, 1988), 6×His containing six His (histidine) residues, 10×His, HA (Influenza agglutinin), human c-myc fragment, VSP-GP fragment, p18HIV fragment, T7-tag, HSV-tag, E-tag, SV40T antigen fragment, lck tag, α-tubulin fragment, B-tag, Protein C fragment, and the like.

Examples of proteins that may be fused to a protein of the invention include GST (glutathione-S-transferase), HA (Influenza agglutinin), immunoglobulin constant region, β-galactosidase, MBP (maltose-binding protein), and such.

Fusion proteins can be prepared by fusing commercially available DNA, encoding the fusion peptides or proteins discussed above, with the DNA encoding the protein of the present invention and expressing the fused DNA prepared.

An alternative method known in the art to isolate functionally equivalent proteins is, for example, the method using a hybridization technique (Sambrook et al., Molecular Cloning 2nd ed. 9.47-9.58, Cold Spring Harbor Lab. Press, 1989). One skilled in the art can readily isolate a DNA having high homology with a whole or part of the DNA sequence (SEQ ID NOs:1, 3, 5 or 7) encoding the human or mouse Gros1 protein, and isolate functionally equivalent proteins to the human or mouse Gros1 protein from the isolated DNA. The proteins of the present invention include those that are encoded by DNA that hybridize with a whole or part of the DNA sequence encoding the human or mouse Gros1 protein and are functionally equivalent to the human or mouse Gros1 protein. These proteins include mammal homologues corresponding to the protein derived from human or mouse (for example, a protein encoded by a monkey, rat, rabbit and bovine gene). In isolating a cDNA highly homologous to the DNA encoding the human or mouse Gros1 protein from animals, it is particularly preferable to use tissues from ovary or testis.

The condition of hybridization for isolating a DNA encoding a protein functionally equivalent to the human or mouse Gros1 protein can be routinely selected by a person skilled in the art. For example, hybridization may be performed by conducting prehybridization at 68° C. for 30 min or longer using “Rapid-hyb buffer” (Amersham LIFE SCIENCE), adding a labeled probe, and warming at 68° C. for 1 hour or longer. The following washing step can be conducted, for example, in a low stringent condition. A low stringent condition is, for example, 42° C., 2×SSC, 0.1% SDS, or preferably 50° C., 2×SSC, 0.1% SDS. More preferably, high stringent conditions are used. A high stringent condition is, for example, washing 3 times in 2×SSC, 0.01% SDS at room temperature for 20 min, then washing 3 times in 1×SSC, 0.1% SDS at 37° C. for 20 min, and washing twice in 1×SSC, 0.1% SDS at 50° C. for 20 min. However, several factors such as temperature and salt concentration can influence the stringency of hybridization and one skilled in the art can suitably select the factors to achieve the requisite stringency.

In place of hybridization, a gene amplification method, for example, the polymerase chain reaction (PCR) method, can be utilized to isolate a DNA encoding a protein functionally equivalent to the human or mouse Gros1 protein, using a primer synthesized based on the sequence information of the DNA (SEQ ID NO:1, 3, 5 or 7) encoding the human or mouse Gros1 protein.

Proteins that are functionally equivalent to the human or mouse Gros1 protein encoded by the DNA isolated through the above hybridization techniques or gene amplification techniques, normally have a high homology to the amino acid sequence of the human or mouse Gros1 protein. “High homology” typically refers to a homology of 40% or higher, preferably 60% or higher, more preferably 80% or higher, even more preferably 95% or higher. The homology of a protein can be determined by following the algorithm in “Wilbur, W. J. and Lipman, D. J. Proc. Natl. Acad. Sci. USA (1983) 80, 726-730”.

A protein of the present invention may have variations in amino acid sequence, molecular weight, isoelectric point, the presence or absence of sugar chains, or form, depending on the cell or host used to produce it or the purification method utilized. Nevertheless, so long as it has a function equivalent to that of the human or mouse Gros1 protein (SEQ ID NO:2, 4, 6 or 8) of the present invention, it is within the scope of the present invention.

The term “substantially pure” as used herein in reference to a given polypeptide means that the polypeptide is substantially free from other biological macromolecules. For example, the substantially pure polypeptide is at least 75%, 80, 85, 95, or 99% pure by dry weight. Purity can be measured by any appropriate standard method known in the art, for example, by column chromatography, polyacrylamide gel electrophoresis, or HPLC analysis.

Accordingly, the invention includes a polypeptide having a sequence shown as SEQ ID NO:2, 4, 6 or 8. The invention also includes a polypeptide, or fragment thereof, that differs from the corresponding sequence shown as SEQ ID NO:2, 4, 6 or 8. The differences are, preferably, differences or changes at a non-essential residue or a conservative substitution. In one embodiment, the polypeptide includes an amino acid sequence at least about 60% identical to a sequence shown as SEQ ID NO:2, 4, 6 or 8, or a fragment thereof Preferably, the polypeptide is at least 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, 99% or more identical to SEQ ID NO:2, 4, 6 or 8 and has at least one cell proliferation related function or activity described herein, e.g., the polypeptide inhibits cell proliferation or decreases colony forming activity. Preferred polypeptide fragments of the invention are at least 10%, preferably at least 20%, 30%, 40%, 50%, 60%, 70%, or more, of the length of the sequence shown as SEQ ID NO:2, 4, 6 or 8 and have at least one cell proliferation related function or activity described herein. Or alternatively, the fragment can be merely an immunogenic fragment.

The proteins of the present invention can be prepared as recombinant proteins or natural proteins, by methods well known to those skilled in the art. A recombinant protein can be prepared by inserting a DNA , which encodes the protein of the present invention (for example, the DNA comprising the nucleotide sequence of SEQ ID NOs:1, 3, 5, or 7), into an appropriate expression vector, introducing the vector into an appropriate host cell, collecting thus obtained recombinants, obtaining the extract thereof, and purifying the protein by subjecting the extract to chromatography, for example, ion exchange chromatography, reverse phase chromatography, gel filtration, or affinity chromatography utilizing a column to which antibodies against the protein of the present invention is fixed, or by combining more than one of aforementioned columns.

Also when the protein of the present invention is expressed within host cells (for example, animal cells and E. coli) as a fusion protein with glutathione-S-transferase protein or as a recombinant protein supplemented with multiple histidines, the expressed recombinant protein can be purified using a glutathione column or nickel column.

After purifying the fusion protein, it is also possible to exclude regions other than the objective protein by cutting with thrombin or factor-Xa as required.

A natural protein can be isolated by methods known to a person skilled in the art, for example, by contacting the affinity column, in which antibodies binding to the Gros1 protein described below are bound, with the extract of tissues or cells expressing the protein of the present invention. The antibodies can be polyclonal antibodies or a monoclonal antibodies.

The present invention also encompasses partial peptides of the protein of the present invention. The partial peptide has an amino acid sequence specific to the protein of the present invention and consists of at least 7 amino acids, preferably 8 amino acids or more, and more preferably 9 amino acids or more. The partial peptide can be used, for example, for preparing antibodies against the protein of the present invention, screening for a compound that binds to the protein of the present invention, and screening for accelerators or inhibitors of the protein of the present invention.

A partial peptide of the invention can be produced by genetic engineering, by known methods of peptide synthesis, or by digesting the protein of the invention with an appropriate peptidase. For peptide synthesis, for example, solid phase synthesis or liquid phase synthesis may be used.

Furthermore, the present invention provides DNA encoding the proteins of the present invention. The DNA of the present invention can be used for the in vivo or in vitro production of the protein of the present invention as described above, or can be applied to gene therapy for diseases attributed to genetic abnormality in the gene encoding the protein of the present invention. Any form of the DNA of the present invention can be used, so long as it encodes the protein of the present invention. Specifically, cDNA synthesized from the mRNA, genomic DNA, and chemically synthesized DNA can be used. The DNA of the present invention include a DNA comprising a given nucleotide sequences as well as its degenerate sequences, so long as the resulting DNA encodes a protein of the present invention.

The DNA of the present invention can be prepared by methods known to a person skilled in the art. For example, the DNA of the present invention can be prepared by: preparing a cDNA library from cells which express the protein of the present invention, and conducting hybridization using a partial sequence of the DNA of the present invention (for example, SEQ ID NOs:1, 3, 5, or 7) as a probe. A cDNA library can be prepared, for example, by the method described in Sambrook et al., Molecular Cloning, Cold Spring Harbor Laboratory Press (1989); alternatively, commercially available cDNA libraries may be used. A cDNA library can be also prepared by: extracting RNAs from cells expressing the protein of the present invention, synthesizing oligo DNAs based on the sequence of the DNA of the present invention (for example, SEQ ID NOs:1, 3, 5 or 7), conducting PCR by using the oligos as primers, and amplifying cDNAs encoding the protein of the present invention.

As used herein, an “isolated nucleic acid” is a nucleic acid, the structure of which is not identical to that of any naturally occurring nucleic acid or to that of any fragment of a naturally occurring genomic nucleic acid spanning more than three genes. The term therefore covers, for example, (a) a DNA which has the sequence of part of a naturally occurring genomic DNA molecule but is not flanked by both of the coding sequences that flank that part of the molecule in the genome of the organism in which it naturally occurs; (b) a nucleic acid incorporated into a vector or into the genomic DNA of a prokaryote or eukaryote in a manner such that the resulting molecule is not identical to any naturally occurring vector or genomic DNA; (c) a separate molecule such as a cDNA, a genomic fragment, a fragment produced by polymerase chain reaction (PCR), or a restriction fragment; and (d) a recombinant nucleotide sequence that is part of a hybrid gene, i.e., a gene encoding a fusion protein. Specifically excluded from this definition are nucleic acids present in random, uncharacterized mixtures of different DNA molecules, transfected cells, or cell clones, e.g., as these occur in a DNA library such as a cDNA or genomic DNA library.

Accordingly, in one aspect, the invention provides an isolated or purified nucleic acid molecule that encodes a polypeptide described herein or a fragment thereof. Preferably, the isolated nucleic acid molecule includes a nucleotide sequence that is at least 60% identical to the nucleotide sequence shown in SEQ ID NO:1, 3, 5 or 7. More preferably, the isolated nucleic acid molecule is at least 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more, identical to the nucleotide sequence shown in SEQ ID NO:1, 3, 5 or 7. In the case of an isolated nucleic acid molecule which is longer than or equivalent in length to the reference sequence, e.g., SEQ ID NO:1, 3, 5 or 7, the comparison is made with the full length of the reference sequence. Where the isolated nucleic acid molecule is shorter that the reference sequence, e.g., shorter than SEQ ID NO:1, 3, 5 or 7, the comparison is made to a segment of the reference sequence of the same length (excluding any loop required by the homology calculation).

As used herein, “% identity” of two amino acid sequences, or of two nucleic acid sequences, is determined using the algorithm of Karlin and Altschul (Proc. Natl. Acad. Sci. USA, 87:2264-2268, 1990), modified as in Karlin and Altschul, Proc. Natl. Acad. Sci. USA, 90:5873-5877, 1993)). Such an algorithm is incorporated into the NBLAST and XBLAST programs of Altschul et al. (J. Mol. Biol., 215:403-410, 1990). BLAST nucleotide searches are performed with the NBLAST program, score=100, wordlength=12. BLAST protein searches are performed with the XBLAST program, score=50, wordlength=3. To obtain gapped alignment for comparison purposes GappedBLAST is utilized as described in Altschul et al. (Nucleic Acids Res., 25:3389-3402, 1997). When utilizing BLAST and GappedBLAST programs the default parameters of the respective programs (e.g., XBLAST and NBLAST) are used to obtain nucleotide sequences homologous to a nucleic acid molecule of the invention.

In addition, by sequencing the nucleotides of the obtained cDNA, the translation region encoded by the cDNA can be determined, and the amino acid sequence of the protein of the present invention can be obtained. Moreover, by screening the genomic DNA library using the obtained cDNA as a probe, the genomic DNA can be isolated.

More specifically, mRNAs may first be prepared from cells, tissue, or organ (for example, ovary, testis, placenta, etc.) in which the protein of the invention is expressed. Known methods can be used to isolate mRNAs; for instance, total RNA may be prepared by guanidine ultracentrifugation (Chirgwin et al., Biochemistry, 18:5294-5299, 1979) or AGPC method (Chomczynski et al., Anal. Biochem., 162:156-159, 1987). In addition, mRNA may be purified from total RNA using mRNA Purification Kit (Pharmacia) and such or, alternatively, mRNA may be directly purified by QuickPrep mRNA Purification Kit (Pharmacia).

The obtained mRNA is used to synthesize cDNA using reverse transcriptase. cDNA may be synthesized by using a commercially available kit, such as the AMV Reverse Transcriptase First-strand cDNA Synthesis Kit (Seikagaku Kogyo). Alternatively, cDNA may be synthesized and amplified following the 5′-RACE method (Frohman et al., Proc. Natl. Acad. Sci. USA,85:8998-9002, 1988; Belyaysky et al., Nucleic Acids Res., 17:2919-2932, 1989), which uses a primer and such, described herein, the 5′-Ampli FINDER RACE Kit (Clontech), and polymerase chain reaction (PCR).

A desired DNA fragment is prepared from the PCR products and ligated with a vector DNA. The recombinant vectors are used to transform E. coli and such, and a desired recombinant vector is prepared from a selected colony. The nucleotide sequence of the desired DNA can be verified by conventional methods, such as dideoxynucleotide chain termination.

The nucleotide sequence of a DNA of the invention may be designed to be expressed more efficiently by taking into account the frequency of codon usage in the host to be used for expression (Grantham et al., Nucleic Acids Res., 9:43-74, 1981). The DNA of the present invention may be altered by a commercially available kit or a conventional method. For instance, the DNA may be altered by digestion with restriction enzymes, insertion of a synthetic oligonucleotide or an appropriate DNA fragment, addition of a linker, or insertion of the initiation codon (ATG) and/or the stop codon (TAA, TGA, or TAG).

Specifically, the DNA of the present invention encompasses the DNA comprising the nucleotide sequence from base A at position 52 to base C at position 1140 of SEQ ID NO: 1; the DNA from base A at position 52 to base A at position 2259 of SEQ ID NO:3; the DNA from base A at position 12 to base G at position 2252 of SEQ ID NO:5; and that from base A at position 12 to base A at position 1640 of SEQ ID NO:3.

Furthermore, the present invention provides a DNA that hybridizes under stringent conditions with a DNA having a nucleotide sequence of SEQ ID NOs:1, 3, 5 or 7, and encodes a protein functionally equivalent to the protein of the invention described above.

One skilled in the art may appropriately choose stringent conditions. For example, low stringent condition can be used. More preferably, high stringent condition can be used. These conditions are the same as those described above. The hybridizing DNA above is preferably a cDNA or a chromosomal DNA.

The present invention also provides a vector into which a DNA of the present invention is inserted. A vector of the present invention is useful to keep a DNA of the present invention in host cell, or to express the protein of the present invention.

When E. coli is a host cell and the vector is amplified and produced in a large amount in E. coli (e.g., JM109, DH5α, HB101, or XL1Blue), the vector should have “ori” to be amplified in E. coli and a marker gene for selecting transformed E. coli (e.g., a drug-resistance gene selected by a drug such as ampicillin, tetracycline, kanamycin, chloramphenicol or the like). For example, M13-series vectors, pUC-series vectors, pBR322, pBluescript, pCR-Script, etc., can be used. In addition, pGEM-T, pDIRECT, and pT7 can also be used for subcloning and extracting cDNA as well as the vectors described above. When a vector is used to produce the protein of the present invention, an expression vector is especially useful. For example, an expression vector to be expressed in E. coli should have the above characteristics to be amplified in E. coli. When E. coli, such as JM109, DH5α, HB101, or XL1 Blue, are used as a host cell, the vector should have a promoter, for example, lacZ promoter (Ward et al., Nature, 341:544-546, 1989; FASEB J, 6:2422-2427, 1992), araB promoter (Better et al., Science, 240:1041-1043, 1988), or T7 promoter or the like, that can efficiently express the desired gene in E. coli. In that respect, pGEX-5X-1 (Pharmacia), “QIAexpress system” (Qiagen), pEGFP and pET (in this case, the host is preferably BL21 which expresses T7 RNA polymerase), for example, can be used instead of the above vectors.

Additionally, the vector may also contain a signal sequence for polypeptide secretion. An exemplary signal sequence that directs the protein to be secreted to the periplasm of the E. coli is the pelB signal sequence (Lei et al., J. Bacteriol., 169: 4379, 1987). Means for introducing the vectors into the target host cells include, for example, the calcium chloride method, and the electroporation method.

In addition to E. coli, for example, expression vectors derived from mammals (for example, pcDNA3 (Invitrogen) and pEGF-BOS (Nucleic Acids. Res., 18(17):5322, 1990), pEF, pCDM8), expression vectors derived from insect cells (for example, “Bac-to-BAC baculovirus expression system” (GIBCO BRL), pBacPAK8), expression vectors derived from plants (for example pMH1, pMH2), expression vectors derived from animal viruses (for example, pHSV, pMV, pAdexLcw), expression vectors derived from retroviruses (for example, pZIpneo), expression vector derived from yeast (for example, “Pichia Expression Kit” (Invitrogen), pNV11, SP-Q01), and expression vectors derived from Bacillus subtilis (for example, pPL608, pKTH50) can be used for producing the protein of the present invention.

In order to express the vector in animal cells, such as CHO, COS, or NIH3T3 cells, the vector should have a promoter necessary for expression in such cells, for example, the SV40 promoter (Mulligan et al., Nature (1979) 277, 108), the MMLV-LTR promoter, the EF1a promoter (Mizushima et al., Nucleic Acids Res. (1990) 18, 5322), the CMV promoter, and the like, and preferably a marker gene for selecting transformants (for example, a drug resistance gene selected by a drug (e.g., neomycin, G418)). Examples of known vectors with these characteristics include, for example, pMAM, pDR2, pBK-RSV, pBK-CMV, pOPRSV, and pOP13.

In addition, methods may be used to express a gene stably and, at the same time, to amplify the copy number of the gene in cells. For example, a vector comprising the complementary DHFR gene (for example pCHO I) may be introduced into CHO cells in which the nucleic acid synthesizing pathway is deleted, and then amplified by methotrexate (MTX). Furthermore, in case of transient expression of a gene, the method wherein a vector comprising a replication origin of SV40 (pcD, etc.) is transfected into COS cells comprising the SV40 T antigen expressing gene on the chromosome can be used.

The DNA of the present invention can further be expressed in vivo in animals, for example, by inserting the DNA of the present invention into an appropriate vector and introducing it into living bodies by methods such as the retrovirus method, the liposome method, the cationic liposome method, and the adenovirus method. In such a manner, gene therapy against diseases attributed to mutation of Gros1 gene of the present invention can be accomplished. As a vector to be used, for example, adenovirus vector (for example pAdexlcw), and retrovirus vector (for example, pZIPneo) can be mentioned, but is not restricted thereto. General gene manipulation, such as insertion of the DNA of the present invention to a vector, can be performed according to conventional methods (Molecular Cloning, 5:61-65. 63). Administration into a living body can be either an ex vivo method, or in vivo method.

The present invention further provides a host cell into which the vector of the present invention has been transfected. The host cell into which the vector of the invention is transfected is not particularly limited. For example, E. coli, various animal cells and such can be used. The host cells of the present invention can be used, for example, as a production system for producing or expressing the protein of the present invention. The present invention provides methods of producing a protein of the invention both in vitro and in vivo. For in vitro production, eukaryotic cells or prokaryotic cells can be used as host cells.

Useful eukaryotic cells may be animal, plant, or fungi cells. Exemplary animal cells include, for example, mammalian cells such as CHO (J. Exp. Med., 108:945, 1995), COS, 3T3, myeloma, baby hamster kidney (BHK), HeLa, or Vero cells, amphibian cells such as Xenopus oocytes (Valle et al., Nature, 291:340-358, 1981), or insect cells such as sf9, sf21, or Tn5 cells. CHO cells lacking DHFR gene (dhfr-CHO) (Proc. Natl. Acad. Sci. USA, 77:4216-4220, 1980) or CHO K-1 (Proc. Natl. Acad. Sci. USA, 60:1275, 1968) may also be used. Of the animal cells, CHO cells are particularly preferable for the mass expression. A vector can be transfected into host cells by, for example, the calcium phosphate method, the DEAE-dextran method, the cationic liposome DOTAP (Boehringer Mannheim), the electroporation method, the lipofection method, and so on.

As plant cells, plant cells originating from Nicotiana tabacum are known as protein-production systems, and may be used as callus cultures. As fungi cells, yeast cells such as Saccharomyces, including Saccharomyces cerevisiae, or filamentous fungi such as Aspergillus, including Aspergillus niger, are known and may be used herein.

Useful prokaryotic cells include bacterial cells, such as E. coli, for example, JM109, DH5a, and HB101. Other bacterial systems include, Bacillus subtilis.

These cells are transformed by a desired DNA, and the resulting transformants are cultured in vitro to obtain the protein. Transformants can be cultured using known methods. Culture medium for animal cells include, for example, DMEM, MEM, RPMI1640, or IMDM may be used with or without serum supplement such as fetal calf serum (FCS). The pH of the culture medium is preferably between about 6 and 8. Such cells are typically cultured at about 30 to 40° C. for about 15 to 200 hr, and the culture medium may be replaced, aerated, or stirred if necessary.

Animal and plant hosts may be used for in vivo production. For example, a desired DNA can be transfected into an animal or plant host. Encoded proteins are produced in vivo, and then recovered. These animal and plant hosts are included in host cells of the present invention.

Animals to be used for the production system described above include, but are not limited to, mammals and insects. Mammals, such as goat, porcine, sheep, mouse, and bovine, may be used (Vicki Glaser, SPECTRUM Biotechnology Applications (1993)). Alternatively, the mammals may be transgenic animals.

For instance, a desired DNA may be prepared as a fusion gene, by fusing it with a gene, such as goat β casein gene which encodes a protein specifically produced into milk. DNA fragments comprising the fusion gene are injected into goat embryos, which are then impregnated into female goats. Proteins are recovered from milk produced by the transgenic goats (i.e., those born from the goats that had received the modified embryos) or from their offspring. To increase the amount of milk containing the proteins produced by transgenic goats, appropriate hormones may be administered to them (Ebert et al., Bio/Technology, 12:699-702, 1994).

Alternatively, insects, such as the silkworm, may be used. A DNA encoding a desired protein inserted into baculovirus can be used to transfect silkworms, and the desired protein may be recovered from their body fluid (Susumu et al., Nature, 315:592-594, 1985).

As plants, for example, tobacco can be used. In use of tobacco, a DNA encoding a desired protein may be inserted into a plant expression vector, such as pMON530, which is introduced into bacteria, such as Agrobacterium tumefaciens. Then, the bacteria is used to transfect a tobacco plant, such as Nicotiana tabacum, and a desired polypeptide is recovered from their leaves (Julian et al., Eur. J. Immunol., 24:131-138, 1994).

A protein of the present invention obtained as above may be isolated from inside or outside (such as medium) of host cells, and purified as a substantially pure homogeneous protein. The method for protein isolation and purification is not limited to any specific method; in fact, any standard method may be used. For instance, column chromatography, filter, ultrafiltration, salt precipitation, solvent precipitation, solvent extraction, distillation, immunoprecipitation, SDS-polyacrylamide gel electrophoresis, isoelectric point electrophoresis, dialysis, and recrystallization may be appropriately selected and combined to isolate and purify the protein.

Examples of chromatography include, for example, affinity chromatography, ion-exchange chromatography, hydrophobic chromatography, gel filtration, reverse phase chromatography, adsorption chromatography, and such (Strategies for Protein Purification and Characterization: A Laboratory Course Manual. Ed. Daniel R. Marshak et al., Cold Spring Harbor Laboratory Press (1996)). These chromatographies may be performed by liquid chromatography, such as HPLC and FPLC. Thus, the present invention provides for highly purified proteins prepared by the above methods.

A protein of the present invention may be optionally modified or partially deleted by treating it with an appropriate protein modification enzyme before or after purification. Useful protein modification enzymes include, but are not limited to, trypsin, chymotrypsin, lysylendopeptidase, protein kinase, glucosidase and so on.

The present invention provides an antibody that binds to the protein of the invention. The antibody of the invention can be used in any form, such as monoclonal or polyclonal antibodies, and includes antiserum obtained by immunizing an animal such as a rabbit with the protein of the invention, all classes of polyclonal and monoclonal antibodies, human antibodies, and humanized antibodies produced by genetic recombination.

A protein of the invention used as an antigen to obtain an antibody may be derived from any animal species, but preferably is derived from a mammal such as a human, mouse, or rat, more preferably from a human. A human-derived protein may be obtained from the nucleotide or amino acid sequences disclosed herein.

According to the present invention, the protein to be used as an immunization antigen may be a complete protein or a partial peptide of the protein. A partial peptide may comprise, for example, the amino (N)-terminal or carboxy (C)-terminal fragment of a protein of the present invention. Herein, an antibody is defined as a protein that reacts with either the full length or a fragment of a protein of the present invention.

A gene encoding a protein of the invention or its fragment may be inserted into a known expression vector, which is then used to transform a host cell as described herein. The desired protein or its fragment may be recovered from the outside or inside of host cells by any standard method, and may subsequently be used as an antigen. Alternatively, cells expressing the protein or their lysates, or a chemically synthesized protein may be used as the antigen.

Any mammalian animal may be immunized with the antigen, but preferably the compatibility with parental cells used for cell fusion is taken into account. In general, animals of Rodentia, Lagomorpha, or Primates are used.

Animals of Rodentia include, for example, mouse, rat, and hamster. Animals of Lagomorpha include, for example, rabbit. Animals of Primates include, for example, a monkey of Catarrhini (old world monkey) such as Macaca fascicularis, rhesus monkey, sacred baboon, and chimpanzees.

Methods for immunizing animals with antigens are known in the art. Intraperitoneal injection or subcutaneous injection of antigens is a standard method for immunization of mammals. More specifically, antigens may be diluted and suspended in an appropriate amount of phosphate buffered saline (PBS), physiological saline, etc. If desired, the antigen suspension may be mixed with an appropriate amount of a standard adjuvant, such as Freund's complete adjuvant, made into emulsion, and then administered to mammalian animals. Preferably, it is followed by several administrations of antigen mixed with an appropriately amount of Freund's incomplete adjuvant every 4 to 21 days. An appropriate carrier may also be used for immunization. After immunization as above, serum is examined by a standard method for an increase in the amount of desired antibodies.

Polyclonal antibodies against the proteins of the present invention may be prepared by collecting blood from the immunized mammal examined for the increase of desired antibodies in the serum, and by separating serum from the blood by any conventional method. Polyclonal antibodies include serum containing the polyclonal antibodies, as well as the fraction containing the polyclonal antibodies may be isolated from the serum. Immunoglobulin G or M can be prepared from a fraction which recognizes only the protein of the present invention using, for example, an affinity column coupled with the protein of the present invention, and further purifying this fraction by using protein A or protein G column.

To prepare monoclonal antibodies, immune cells are collected from the mammal immunized with the antigen and checked for the increased level of desired antibodies in the serum as described above, and are subjected to cell fusion. The immune cells used for cell fusion are preferably obtained from spleen. Other preferred parental cells to be fused with the above immunocyte include, for example, myeloma cells of mammalians, and more preferably myeloma cells having an acquired property for the selection of fused cells by drugs.

The above immunocyte and myeloma cells can be fused according to known methods, for example, the method of Milstein et al. (Galfre et al., Methods Enzymol., 73:3-46, 1981).

Resulting hybridomas obtained by the cell fusion may be selected by cultivating them in a standard selection medium, such as HAT medium (hypoxanthine, aminopterin, and thymidine containing medium). The cell culture is typically continued in the HAT medium for several days to several weeks, the time being sufficient to allow all the other cells, with the exception of the desired hybridoma (non-fused cells), to die. Then, the standard limiting dilution is performed to screen and clone a hybridoma cell producing the desired antibody.

In addition to the above method in which a non-human animal is immunized with an antigen for preparing hybridoma, a hybridoma producing a desired human antibody that is able to bind to the protein can be obtained by the following method. First, human lymphocytes such as those infected by EB virus may be immunized with a protein, protein expressing cells, or their lysates in vitro. Then, the immunized lymphocytes are fused with human-derived myeloma cells that are capable of indefinitely dividing, such as U266, to yield the desired hybridoma (Unexamined Published Japanese Patent Application No. (JP-A) Sho 63-17688).

The obtained hybridomas are subsequently transplanted into the abdominal cavity of a mouse and the ascites are harvested. The obtained monoclonal antibodies can be purified by, for example, ammonium sulfate precipitation, a protein A or protein G column, DEAE ion exchange chromatography, or an affinity column to which the protein of the present invention is coupled. The antibody of the present invention can be used not only for purification and detection of the protein of the present invention, but also as a candidate for agonists and antagonists of the protein of the present invention. In addition, this antibody can be applied to the antibody treatment for diseases related to the protein of the present invention. When the obtained antibody is to be administered to the human body (antibody treatment), a human antibody or a humanized antibody is preferable for reducing immunogenicity.

For example, transgenic animals having a repertory of human antibody genes may be immunized with an antigen selected from a protein, protein expressing cells, or their lysates. Antibody producing cells are then collected from the animals and fused with myeloma cells to obtain hybridoma, from which human antibodies against the protein can be prepared (see WO92-03918, WO93-2227, WO94-02602, WO94-25585, WO96-33735, and WO96-34096).

Alternatively, an immune cell, such as an immunized lymphocyte, producing antibodies may be immortalized by an oncogene and used for preparing monoclonal antibodies.

Monoclonal antibodies thus obtained can be also recombinantly prepared using genetic engineering techniques (see, for example, Borrebaeck C. A. K. and Larrick J. W. Therapeutic Monoclonal Antibodies, published in the United Kingdom by MacMillan Publishers LTD (1990)). A DNA encoding an antibody may be cloned from an immune cell, such as a hybridoma or an immunized lymphocyte producing the antibody, inserted into an appropriate vector, and introduced into host cells to prepare a recombinant antibody. The present invention also provides recombinant antibodies prepared as described above.

Furthermore, an antibody of the present invention may be a fragment of an antibody or modified antibody, so long as it binds to one or more of the proteins of the invention. For instance, the antibody fragment may be Fab, F(ab′)₂, Fv, or single chain Fv (scFv), in which Fv fragments from H and L chains are ligated by an appropriate linker (Huston et al., Proc. Natl. Acad. Sci. USA, 85:5879-5883, 1988). More specifically, an antibody fragment may be generated by treating an antibody with an enzyme, such as papain or pepsin. Alternatively, a gene encoding the antibody fragment may be constructed, inserted into an expression vector, and expressed in an appropriate host cell (see, for example, Co et al., J. Immunol., 152:2968-2976, 1994; Better et al., Methods Enzymol., 178:476-496, 1989; Pluckthun et al., Methods Enzymol., 178:497-515, 1989; Lamoyi, Methods Enzymol., 121:652-663, 1986; Rousseaux et al., Methods Enzymol., 121:663-669, 1986; Bird et al., Trends Biotechnol., 9:132-137, 1991).

An antibody may be modified by conjugation with a variety of molecules, such as polyethylene glycol (PEG). The present invention provides for such modified antibodies. The modified antibody can be obtained by chemically modifying an antibody. These modification methods are conventional in the field.

Alternatively, an antibody of the present invention may be obtained as a chimeric antibody, between a variable region derived from nonhuman antibody and the constant region derived from human antibody, or as a humanized antibody, comprising the complementarity determining region (CDR) derived from nonhuman antibody, the frame work region (FR) derived from human antibody, and the constant region. Such antibodies can be prepared by using known technology.

Antibodies obtained as above may be purified to homogeneity. For example, the separation and purification of the antibody can be performed according to separation and purification methods used for general proteins. For example, the antibody may be separated and isolated by the appropriately selected and combined use of column chromatographies, such as affinity chromatography, filter, ultrafiltration, salting-out, dialysis, SDS polyacrylamide gel electrophoresis, isoelectric focusing, and others (Antibodies: A Laboratory Manual. Ed Harlow and David Lane, Cold Spring Harbor Laboratory, 1988), but are not limited thereto.

A protein A column and protein G column can be used as the affinity column. Exemplary protein A columns to be used include, for example, Hyper D, POROS, and Sepharose F.F. (Pharmacia). Exemplary chromatography, with the exception of affinity includes, for example, ion-exchange chromatography, hydrophobic chromatography, gel filtration, reverse-phase chromatography, adsorption chromatography, and the like (Strategies for Protein Purification and Characterization: A Laboratory Course Manual. Ed Daniel R. Marshak et al., Cold Spring Harbor Laboratory Press, 1996). The chromatographic procedures can be carried out by liquid-phase chromatography, such as HPLC, FPLC.

For example, measurement of absorbance, enzyme-linked immunosorbent assay (ELISA), enzyme immunoassay (EIA), radioimmunoassay (RIA), and/or immunofluorescence may be used to measure the antigen binding activity of the antibody of the invention. In ELISA, the antibody of the present invention is immobilized on a plate, protein of the invention is applied to the plate, and then a sample containing a desired antibody, such as culture supernatant of antibody producing cells or purified antibodies, is applied. Then, a secondary antibody that recognizes the primary antibody and is labeled with an enzyme, such as alkaline phosphatase, is applied, and the plate is incubated. Next, after washing, an enzyme substrate, such as p-nitrophenyl phosphate, is added to the plate, and the absorbance is measured to evaluate the antigen binding activity of the sample. A fragment of the protein, such as a C-terminal or N-terminal fragment may be used as a protein. BIAcore (Pharmacia) may be used to evaluate the activity of the antibody according to the present invention.

The above methods allow for the detection or measurement of the protein of the invention, by exposing the antibody of the invention to a sample assumed to contain the protein of the invention, and detecting or measuring the immune complex formed by the antibody and the protein.

Because the method of detection or measurement of the protein according to the invention can specifically detect or measure a protein, the method may be useful in a variety of experiments in which the protein is used.

The present invention also provides a polynucleotide which hybridizes with the DNA encoding human or mouse Gros1 protein (SEQ ID NOs:1, 3, 5, or 7) or the complementary strand thereof, and which comprises at least 15 nucleotides. The polynucleotide of the present invention is preferably a polynucleotide which specifically hybridizes with the DNA encoding the protein of the present invention. The term “specifically hybridize” as used herein, means that cross-hybridization does not occur significantly with DNA encoding other proteins, under the usual hybridizing conditions, preferably under stringent hybridizing conditions. Such polynucleotides include, probes, primers, nucleotides and nucleotide derivatives (for example, antisense oligonucleotides and ribozymes), which specifically hybridize with DNA encoding the protein of the invention or its complementary strand. Moreover, such polynucleotide can be utilized for the preparation of DNA chip.

The present invention includes an antisense oligonucleotide that hybridizes with any site within the nucleotide sequence any one of SEQ ID NO:1, 3, 5 or 7. This antisense oligonucleotide is preferably against at least 15 continuous nucleotides of the nucleotide sequence any one of SEQ ID NO:1, 3, 5 or 7. The above-mentioned antisense oligonucleotide, which contains an initiation codon in the above-mentioned at least 15 continuous nucleotides, is even more preferred.

Derivatives or modified products of antisense oligonucleotides can be used as antisense oligonucleotides. Examples of such modified products include lower alkyl phosphonate modifications such as methyl-phosphonate-type or ethyl-phosphonate-type, phosphorothioate modifications and phosphoroamidate modifications.

The term “antisense oligonucleotides” as used herein means, not only those in which the nucleotides corresponding to those constituting a specified region of a DNA or mRNA are entirely complementary, but also those having a mismatch of one or more nucleotides, as long as the DNA or mRNA and the antisense oligonucleotide can specifically hybridize with the nucleotide sequence of SEQ ID NO:1, 3, 5 or 7.

Such polynucleotides are contained as those having, in the “at least 15 continuous nucleotide sequence region”, a homology of at least 70% or higher, preferably at 80% or higher, more preferably 90% or higher, even more preferably 95% or higher. The algorithm stated herein can be used to determine the homology. Such polynucleotides are useful as probes for the isolation or detection of DNA encoding the protein of the invention as stated in a later example or as a primer used for amplifications.

The antisense oligonucleotide derivatives of the present invention act upon cells producing the protein of the invention by binding to the DNA or mRNA encoding the protein, inhibiting its transcription or translation, promoting the degradation of the mRNA, and inhibiting the expression of the protein of the invention, thereby resulting in the inhibition of the protein's function.

An antisense oligonucleotide derivative of the present invention can be made into an external preparation, such as a liniment or a poultice, by mixing with a suitable base material which is inactive against the derivatives.

Also, as needed, the derivatives can be formulated into tablets, powders, granules, capsules, liposome capsules, injections, solutions, nose-drops and freeze-drying agents by adding excipients, isotonic agents, solubilizers, stabilizers, preservatives, pain-killers, and such. These can be prepared by following usual methods.

The antisense oligonucleotide derivative is given to the patient by directly applying onto the ailing site or by injecting into a blood vessel so that it will reach the site of ailment. An antisense-mounting medium can also be used to increase durability and membrane-permeability. Examples are, liposome, poly-L-lysine, lipid, cholesterol, lipofectin or derivatives of these.

The dosage of the antisense oligonucleotide derivative of the present invention can be adjusted suitably according to the patient's condition and used in desired amounts. For example, a dose range of 0.1 to 100 mg/kg, preferably 0.1 to 50 mg/kg can be administered.

The antisense oligonucleotide of the invention inhibits the expression of the protein of the invention and is thereby useful for suppressing the biological activity of the protein of the invention. Also, expression-inhibitors, comprising the antisense oligonucleotide of the invention, are useful in the point that they can inhibit the biological activity of the protein of the invention.

Moreover, the present invention provides a method of screening for a compound that binds to the protein of the present invention by using the protein of the present invention. This screening method comprises the steps of: (a) contacting the protein of the present invention or a partial peptide thereof with a subject sample, (b) detecting the binding activity between the protein of the present invention or the partial peptide thereof and the subject sample, and (c) selecting a compound that binds to the protein of the present invention or the partial peptide thereof.

The protein of the present invention to be used for screening may be a recombinant protein or a protein derived from the nature, or a partial peptide thereof. Any subject sample, for example, cell extracts, cell culture supernatant, products of fermenting microorganism, extracts from marine organism, plant extracts, purified or crude proteins, peptides, non-peptide compounds, synthetic micromolecular compounds and natural compounds, can be used. The protein of the present invention to be contacted with a subject sample can be, for example, a purified protein, a soluble protein, a form bound to a carrier, or a fusion protein fused with other proteins. As a method of screening for proteins, for example, that bind to the protein of the present invention using the protein of the present invention, many methods well known by a person skilled in the art can be used. Such a screening can be conducted by, for example, immunoprecipitation method, specifically, in the following manner. The gene encoding the protein of the present invention is expressed in animal cells and so on by inserting the gene to an expression vector for foreign genes, such as pSV2neo, pcDNA I, and pCD8. The promoter to be used for the expression may be any promoter that can be used commonly and include, for example, the SV40 early promoter (Rigby in Williamson (ed.), Genetic Engineering, vol. 3. Academic Press, London, p. 83-141 (1982)), the EF-1α promoter (Kim et al., Gene, 91:217-223, 1990), the CAG promoter (Niwa et al., Gene, 108:193-200, 1991), the RSV LTR promoter (Cullen, Methods in Enzymology, 152:684-704, 1987) the SRα promoter (Takebe et al., Mol. Cell. Biol., 8:466, 1988), the CMV immediate early promoter (Seed et al., Proc. Natl. Acad. Sci. USA, 84:3365-3369, 1987), the SV40 late promoter (Gheysen et al., J. Mol. Appl. Genet., 1:385-394, 1982), the Adenovirus late promoter (Kaufman et al., Mol. Cell. Biol., 9:946, 1989), the HSV TK promoter and so on. The introduction of the gene into animal cells to express a foreign gene can be performed according to any methods, for example, the electroporation method (Chu et al., Nucl. Acids Res., 15:1311-1326, 1987), the calcium phosphate method (Chen et al., Mol. Cell. Biol., 7:2745-2752, 1987), the DEAE dextran method (Lopata et al., Nucl. Acids Res., 12:5707-5717, 1984; Sussman et al., Mol. Cell. Biol., 4:1642-1643, 1985), the Lipofectin method (Derijard, Cell, 7:1025-1037, 1994; Lamb et al., Nature Genetics, 5:22-30, 1993; Rabindran et al., Science, 259:230-234, 1993), and so on. The protein of the present invention can be expressed as a fusion protein comprising a recognition site (epitope) of a monoclonal antibody by introducing the epitope of the monoclonal antibody, whose specificity has been revealed, to the N- or C-terminus of the protein of the present invention. A commercially available epitope-antibody system can be used (Experimental Medicine, 13:85-90, 1995). Vectors which can express a fusion protein with, for example, β-galactosidase, maltose binding protein, glutathione S-transferase, green florescence protein (GFP) and so on by the use of its multiple cloning sites are commercially available.

A fusion protein prepared by introducing only small epitopes consisting of several to a dozen amino acids so as not to change the property of the protein of the present invention by the fusion is also reported. Epitopes, such as polyhistidine (His-tag), influenza aggregate HA, human c-myc, FLAG, Vesicular stomatitis virus glycoprotein (VSV-GP), T7 gene 10 protein (T7-tag), human simple herpes virus glycoprotein (HSV-tag), E-tag (an epitope on monoclonal phage), and such, and monoclonal antibodies recognizing them can be used as the epitope-antibody system for screening proteins binding to the protein of the present invention (Experimental Medicine, 13:85-90, 1995).

In immunoprecipitation, an immune complex is formed by adding these antibodies to cell lysate prepared by using an appropriate detergent. The immune complex consists of the protein of the present invention, a protein comprising the binding ability with the protein, and an antibody. Immunoprecipitation can be also conducted by using antibodies against the protein of the present invention, besides using antibodies against the above epitopes. An antibody against the protein of the present invention can be prepared, for example, by introducing a gene encoding the protein of the present invention to an appropriate E. coli expression vector, expressing the gene in E. coli, purifying the expressed protein, and immunizing rabbits, mice, rats, goats, domestic fowls and such against the protein. The antibody can be also prepared by immunizing the above animals against a synthesized partial peptide of the protein of the present invention.

An immune complex can be precipitated, for example by Protein A Sepharose or Protein G sepharose when the antibody is a mouse IgG antibody. If the protein of the present invention is prepared as a fusion protein with an epitope, such as GST, an immune complex can be formed in the same manner as in the use of the antibody against the protein of the present invention, by using a substance specifically binding to these epitopes, such as glutathione-Sepharose 4B.

Immunoprecipitation can be performed by following or according to, for example, the methods in the literature (Harlow, E. and Lane, D.: Antibodies pp. 511-552, Cold Spring Harbor Laboratory publications, New York (1988))

SDS-PAGE is commonly used for analysis of immunoprecipitated proteins and the bound protein can be analyzed by the molecular weight of the protein by using gels with an appropriate concentration. Since the protein bound to the protein of the present invention is difficult to detect by a common staining method, such as Coomassie staining or silver staining, the detection sensitivity for the protein can be improved by culturing cells in culture medium containing radioactive isotope, ³⁵S-methionine or ³⁵S-cystein, labeling proteins in the cells, and detecting the proteins. The target protein can be purified directly from the SDS-polyacrylamide gel and its sequence can be determined, when the molecular weight of a protein has been revealed.

As a method for isolating proteins binding to the protein of the present invention by using the protein, for example, West-Western blotting analysis (Skolnik et al., Cell, 65:83-90, 1991) can be used. Specifically, a protein binding to the protein of the present invention can be obtained by preparing a cDNA library from cells, tissues, organs (for example, tissues such as ovary, testis, and placenta or cultured cells) expected to express a protein binding to the protein of the present invention by using a phage vector (λgt11, ZAP, etc.), expressing the protein on LB-agarose, fixing the protein expressed on a filter, reacting the purified and labeled protein of the present invention with the above filter, and detecting the plaques expressing proteins bound to the protein of the present invention according to the label. The protein of the invention may be labeled by utilizing the binding between biotin and avidin, or by utilizing an antibody that specifically binds to the protein of the present invention, or a peptide or polypeptide (for example, GST) that is fused to the protein of the present invention. Methods using radioisotope or fluorescence and such may be also used.

Alternatively, in another embodiment of the screening method of the present invention, a two-hybrid system utilizing cells may be used (“MATCHMAKER Two-Hybrid system”, “Mammalian MATCHMAKER Two-Hybrid Assay Kit”, “MATCHMAKER one-Hybrid system” (Clontech); “HybriZAP Two-Hybrid Vector System” (Stratagene); the references “Dalton S, and Treisman R (1992) Cell 68, 597-612”, “Fields S. and Sternglanz R. Trends Genet. (1994) 10:286-292”).

In the two-hybrid system, the protein of the invention is fused to the SRF-binding region or GAL4-binding region and expressed in yeast cells. A cDNA library is prepared from cells expected to express a protein binding to the protein of the invention, such that the library, when expressed, is fused to the VP16 or GAL4 transcriptional activation region. The cDNA library is then introduced into the above yeast cells and the cDNA derived from the library is isolated from the positive clones detected (when a protein binding to the protein of the invention is expressed in yeast cells, the binding of the two activates a reporter gene, making positive clones detectable). A protein encoded by the cDNA can be prepared by introducing the cDNA isolated above to E. coli and expressing the protein.

As a reporter gene, for example, Ade2 gene, lacZ gene, CAT gene, luciferase gene and such can be used besides HIS3 gene.

A compound binding to the protein of the present invention can be screened using affinity chromatography. For example, the protein of the invention may be immobilized on a carrier of an affinity column, and a test sample, containing a protein capable of binding to the protein of the invention is supposed to be expressed, is applied to the column. A test sample herein may be, for example, cell extracts, cell lysates, etc. After loading the test sample, the column is washed, and proteins bound to the protein of the invention can be prepared.

The amino acid sequence of the obtained protein is analyzed, an oligo DNA is synthesized based on the sequence, and cDNA libraries are screened using the oligo DNA as a probe to obtain a DNA encoding the protein.

A biosensor using the surface plasmon resonance phenomenon may be used as a mean for detecting or quantifying the bound compound in the present invention. When such a biosensor is used, the interaction between the protein of the invention and a test compound can be observed real-time as a surface plasmon resonance signal, using only a minute amount of protein and without labeling (for example, BIAcore, Pharmacia). Therefore, it is possible to evaluate the binding between the protein of the invention and a test compound using a biosensor such as BIAcore.

The methods of screening for molecules that bind when the immobilized protein of the present invention is exposed to synthetic chemical compounds, or natural substance banks, or a random phage peptide display library, or the methods of screening using high-throughput based on combinatorial chemistry techniques (Wrighton et al., Science (US), 273:458-64, 1996; Verdine, Nature (England), 384:11-13, 1996; Hogan, Nature (England), 384:17-19, 1996) to isolate not only proteins but chemical compounds that bind to protein of the present invention (including agonist and antagonist) are well known to one skilled in the art.

A compound isolated by the screening is a candidate for drugs which promote or inhibit the activity of the protein of the present invention, for treating or preventing diseases attributed to, for example, the functional abnormality of the protein of the present invention, or cell proliferative diseases such as cancer. A compound in which a part of the structure of the compound obtained by the present screening method having the activity of binding to the protein of the present invention is converted by addition, deletion and/or replacement, is included in the compounds obtained by the screening method of the present invention.

Moreover the present invention provides a method for screening a compound which promotes or inhibits the activity of the protein of the present invention. Since the Gros1 protein of the present invention has the activity of inhibiting cell proliferation, a compound which promotes or inhibits this activity of Gros1 protein of the present invention can be screened using this activity as an index.

This screening method includes the steps of: (a) culturing cells which express Gros1 protein in the presence of the subject sample, (b) detecting the proliferation of the cells, and (c) selecting a compound which promotes or inhibits the proliferation in comparison with the proliferation detected in the absence of the subject sample.

Any Gros1 proteins can be used for screening so long as they comprise the activity of inhibiting cell proliferation. For example, human or mouse Gros1-L protein can be used and proteins functionally equivalent to these proteins can also be used. Gros1 proteins may be expressed endogenously or exogenously by cells.

Any subject samples, for example, cell extracts, cell culture supernatant, products of fermenting microorganism, extracts of marine organism, plant extracts, purified or crude proteins, peptides, non-peptide compounds, synthetic micromolecular compounds, natural compounds, can be used. A compound obtained by the above screening for compounds that bind to the protein of the present invention can be also used as the subject compound.

The compound isolated by this screening is a candidate for agonists or antagonists of the protein of the present invention. The term “agonist” refers to molecules that activate the function of the protein of the present invention by binding thereto. Likewise, the term “antagonist” refers to molecules that inhibit the function of the protein of the present invention by binding thereto. Moreover, a compound isolated by this screening is a candidate for compounds which inhibit the in vivo interaction of the protein of the present invention with molecules (including DNAs and proteins).

Cell proliferation can be detected, for example, by determining the speed of cell proliferation, measuring the cell cycle and such, as well as by measuring the colony forming activity as described in the Examples.

The compound isolated by the screening is a candidate for drugs which promote or inhibit the activity of the protein of the present invention and can be applied to the treatment for diseases (for example, cancer, etc.) associated with the protein of the present invention.

Moreover, compound in which a part of the structure of the compound promoting or inhibiting the activity of Gros1 proteins is converted by addition, deletion and/or replacement are also included in the compounds obtainable by the screening method of the present invention.

When administrating the compound isolated by the method of the invention as a pharmaceutical for humans and other mammals, such as mice, rats, guinea-pigs, rabbits, chicken, cats, dogs, sheep, pigs, cattle, monkeys, baboons, chimpanzees, the isolated compound can be directly administered or can be formulated into a dosage form using known pharmaceutical preparation methods. For example, according to the need, the drugs can be taken orally, as sugar-coated tablets, capsules, elixirs and microcapsules, or non-orally, in the form of injections of sterile solutions or suspensions with water or any other pharmaceutically acceptable liquid. For example, the compounds can be mixed with pharmacologically acceptable carriers or medium, specifically, sterilized water, physiological saline, plant-oil, emulsifiers, suspending agents, surfactants, stabilizers, flavoring agents, excipients, vehicles, preservatives, binders and such, in a unit dose form required for generally accepted drug implementation. The amount of active ingredients in these preparations makes a suitable dosage within the indicated range acquirable.

Examples of additives that can be mixed to tablets and capsules are, binders such as gelatin, corn starch, tragacanth gum and arabic gum; excipients such as crystalline cellulose; swelling agents such as corn starch, gelatin and alginic acid; lubricants such as magnesium stearate; sweeteners such as sucrose, lactose or saccharin; flavoring agents such as peppermint, Gaultheria adenothrix oil and cherry. When the unit dosage form is a capsule, a liquid carrier, such as oil, can also be further included in the above ingredients. Sterile composites for injections can be formulated following normal drug implementations using vehicles such as distilled water used for injections.

Physiological saline, glucose, and other isotonic liquids including adjuvants, such as D-sorbitol, D-mannnose, D-mannitol, and sodium chloride, can be used as aqueous solutions for injections. These can be used in conjunction with suitable solubilizers, such as alcohol, specifically ethanol, polyalcohols such as propylene glycol and polyethylene glycol, non-ionic surfactants, such as Polysorbate 80™ and HCO-50.

Sesame oil or Soy-bean oil can be used as a oleaginous liquid and may be used in conjunction with benzyl benzoate or benzyl alcohol as a solubilizers and may be formulated with a buffer, such as phosphate buffer and sodium acetate buffer; a pain-killer, such as procaine hydrochloride; a stabilizer, such as benzyl alcohol, phenol; and an anti-oxidant. The prepared injection may be filled into a suitable ampule.

Methods well known to one skilled in the art may be used to administer the inventive pharmaceutical compound to patients, for example as intraarterial, intravenous, percutaneous injections and also as intranasal, transbronchial, intramuscular or oral administrations. The dosage and method of administration vary according to the body-weight and age of a patient and the administration method; however, one skilled in the art can routinely select them. If said compound is encodable by a DNA, the DNA can be inserted into a vector for gene therapy and the vector administered to perform the therapy. The dosage and method of administration vary according to the body-weight, age, and symptoms of a patient but one skilled in the art can select them suitably.

For example, although there are some differences according to the symptoms, the dose of a compound that binds with the protein of the present invention and regulates its activity is about 0.1 mg to about 100 mg per day, preferably about 1.0 mg to about 50 mg per day and more preferably about 1.0 mg to about 20 mg per day, when administered orally to a normal adult (weight 60 kg).

When administering parenterally, in the form of an injection to a normal adult (weight 60 kg), although there are some differences according to the patient, target organ, symptoms and method of administration, it is convenient to intravenously inject a dose of about 0.01 mg to about 30 mg per day, preferably about 0.1 to about 20 mg per day and more preferably about 0.1 to about 10 mg per day. Also, in the case of other animals too, it is possible to administer an amount converted to 60 kgs of body-weight.

All publications and patents cited herein are incorporated by reference in their entirety.

DESCRIPTION OF DRAWINGS

FIG. 1 shows the alignments for the mouse Gros1 sequence and the EST sequence.

FIG. 2 shows the splicing form for cDNA of mouse Gros1.

FIG. 3 shows the splicing form for cDNA of human Gros1.

FIG. 4 shows a photograph indicating the result of Northern analysis in mouse tissues using the mouse Gros1 cDNA probe.

FIG. 5 shows photographs indicating the result of Northern analysis in human cells using the mouse Gros1 cDNAprobe.

FIG. 6 shows a photograph indicating the result of Northern analysis in human tissues using the mouse Gros1 cDNAprobe.

FIG. 7 shows a photograph indicating the result of Western analysis for human GFP-Gros1L and GFP-Gros1S expressed in COS7.

FIG. 8 shows photographs indicating localization of human GFP-Gros1L and human GFP-Gros1S in cells.

FIG. 9 shows photographs depicting the result of Northern analysis in NIH3T3 cells to which mouse Gros1L, Gros1 mutant and Gros1 antisense were introduced.

FIG. 10 shows the result of analysis of colony forming activity of NIH3T3 cells to which mouse Gros1L, Gros1 mutant and Gros1 antisense were introduced.

DETAILED DESCRIPTION

The present invention is illustrated in details by following Examples, but is not restricted to these Examples.

EXAMPLE 1 Cloning and Sequence of Gros1 cDNA

It is known that the comparison of the proteins contained in the Triton X-100 insoluble factions of the plasma membrane of mouse normal cells (CMEF) and immortalized cells (NIH3T3) revealed that the protein (p33), about 30 kDa in size, present in NIH3T3 is not contained in CMEF (Wadhwa et al., Mutat. Res., 256:243-254, 1991). This protein was isolated by SDS-PAGE and anti-p33 polyclonal antibody was prepared by a standard method. A novel gene Gros1-L was obtained from an RS-4 cell cDNA library (Wadhwa et al., J. Biol. Chem., 268:6615-6621, 1993) by immunoscreening using this antibody. The sequence of this gene was novel, and no homologous sequences were found in the DNA sequence data bank. Screening of the human testis library (prepared based on pCMV-SPORT (GIBCO BRL Cat. # 10419-018); D′Alessio et al., Focus, 12:47, 1990; Kriegler, M., 1990, Gene Transfer and Expression: A Laboratory Manual, Stockton Press, New York, N.Y.; Sambrook, J. et al., 1989, Molecular Cloning: A Laboratory Manual, 2^(nd) Edition. Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.; Li et al., BioTechniques, 16:722, 1994) using a ³²P labeled mouse Gros1 probe identified two types of clones (human Gros1-L and Gros1-S). Mouse Gros1-S was identified by searching the EST data using the nucleotide sequences of the obtained mouse Gros1 cDNA fragments and connecting overlapped clones (FIG. 1). This EST contained a 94 by deletion in comparison with mouse Gros1-L or other ESTs, and was predicted to generate a protein (mouse Gros1-S) shorter than the non-deleted type (mouse Gros1-L).

SEQ ID NOs:5 and 7 show the full length nucleotide sequences of mouse Gros1-L cDNA and the full length nucleotide sequence of mouse Gros1-S cDNA obtained by the cloning using EST search, respectively. Amino acid sequences deduced from these nucleotide sequences are shown in SEQ ID NOs:6 and 8, respectively. It was revealed that each of the obtained full-length cDNA sequences shared 85.9% homology with the novel basement membrane-associated proteoglycan (leprecan) isolated from rat cDNA in the DNA sequence data bank. The cDNA obtained by immunoscreening (mouse Gros1-L) and the cDNA obtained by the cloning using EST search encoded a mouse Gros1-S, an 85 kDa protein consisting of 747 amino acids and a 61.5 kDa protein consisting of 542 amino acids (FIG. 2), respectively, having 90.9% homology with the rat leprecan in the protein data bank. Moreover, the above human 3.0 Kb clone cDNA (SEQ ID NO:1) and the cDNA of 2.7 kb clone (SEQ ID NO:3) having 83.9% homology with the mouse Gros1 were revealed to have 81.9% homology with the rat leprecan in the DNA sequence data bank. The obtained 3.0 Kb clone cDNA (SEQ ID NO:1) encoded human Gros1-S of 41 kDa consisting of 363 amino acids (SEQ ID NO:2), and the 2.7 Kb clone cDNA (SEQ ID NO:3) encoded human Gros1-L of 83 kDa consisting of 736 amino acids (SEQ ID NO:4) (FIG. 3), each having 83.0% homology with the leprecan within the protein databank. Although no matching DNA sequences were found, analysis of amino acid sequences by motif search revealed that the amino acid sequences in mouse and human Gros1-L partially comprise the leucine zipper structure frequently found in transcriptional factors.

EXAMPLE 2 Preparation of Recombinant Gros1

The cDNA at 183-1055 within the mouse Gros1-L cDNA open reading frame was amplified by the PCR reaction (94° C. for 1 min, 55° C. for 1 min, and 72° C. for 3 min, 25 cycles) using a sense primer comprising the BamHI site (SEQ ID NO:9) and an antisense primer comprising the HindIII site (SEQ ID NO:10), and the obtained product was inserted into pGEM-T easy vector (Promega) using Rapid Ligation Kit (Boehringer Mannheim). The mixture solution of E. coli JM109 competent cells (TOYOBO) and the vector were treated at 42° C. for 1 min, spread on an ampicillin plate, and cultured for 1 day, and colonies were collected for cloning. To prepare the histidine-tagged protein, the cloned pGEM-T/Gros1 vector was cleaved at BamH I-Hind III sites, ligated with pQE30 (Qiagen), and digested at the same restriction sites by the same manner as above, and colonies were collected to obtain plasmids. E. coli M15 (Qiagen) was cultured until the absorbance at 580 nm reached 0.6, at which point the cells were transformed by the collected plasmids, and proteins were produced by inducing at 37° C. for 3 hours with 0.2 mM IPTG. Lysate of this E. coli was separated by SDS-PAGE method and detection was conducted by the Western blot analysis with the histidine antibody and Gros1 antibody described below. As a result, it was confirmed that a 40 kDa protein was synthesized. The size of the recombinant protein was as predicted. No signals could be detected by the Western blot analysis using the anti-p33 polyclonal antibody in the same manner.

EXAMPLE 3 Northern Blot Analysis

Northern blot analysis was conducted by purchasing a membrane on which 2 μg of mRNA from various mouse, human tissues per lane were loaded (Clontech laboratories, Palo alto, Calif.). The gene fragment of mouse Gros1-L plasmid was used as a probe. Condition for the hybridization was as follows: “Rapid-hyb buffer” (Amersham LIFE SCIENCE) was used, and after prehybridization at 68° C. for 30 min, the labeled probes were added, and the solution was incubated at 68° C. for 2 hours to perform hybridization. Then washing was conducted 3 times in 2×SSC, 0.01% SDS at room temperature for 20 min, then 3 times in 1×SSC, 0.1% SDS at 37° C. for 20 min, and twice in 1×SSC, 0.1% SDS at 50° C. for 20 min. Detection was performed by autoradiography. Northern blot analysis showed that the 4.4 kb and 2.5 kb bands were weakly expressed in most tissues in human, except for testis, ovary, and placenta. In contrast, in testis, ovary, and placenta, very strong expression was observed (FIG. 4). Higher expression of mRNA in human cultured cells was observed than in tissues. Moreover, in human normal cultured cells, the expression amount of the 2.5 kb mRNA was nearly 10 times as high as that for the mRNA of 4.4 kb (FIG. 5). In mouse, the 3.5 kb and 2.5 kb bands were weakly expressed in most tissues, except for brain, spleen and testis. No expression was observed in brain or spleen, and in testis only the 2.5 kb band was expressed. In testis and ovary, only the short type of Gros1 mRNAs was detected. It was shown that the expression dramatically disappeared at the 11^(th) day during developmental process (FIG. 6).

EXAMPLE 4 Location on the Chromosomes

The locations of the genes of the present invention were determined by using a sense primer (SEQ ID NO:11) and an antisense primer (SEQ ID NO:12) specific to human Gros1, with a radiation hybrid panel. As a result, they were found to be present on chromosome 1p31 in human. In mouse, they were deduced to be present on chromosome 4.

EXAMPLE 5 Preparation of Antibodies Specifically Binding to the Gros1 Proteins

Antibodies against the recombinant protein deduced from the gene sequence of Gros1 were prepared. Specifically, the recombinant mouse Gros1-L protein with the histidine-tag prepared in Example 2 was purified by a nickel column; rabbits were immunized to extract the serum 4 times stepwise; and, finally, exsanguinations were conducted. Polyclonal antibodies were prepared by purifying this serum using the protein A column. It was confirmed that this anti-Gros1 polyclonal antibody recognizes Gros1 protein by separating the recombinant histidine-tagged human Gros1-L protein on the gel by SDS-PAGE, and detecting by the Western blot analysis.

EXAMPLE 6 Western Blot Analysis

Western blot analysis on the lysate of human normal lung fibroblast cell, MRC-5, with the above Gros1 polyclonal antibodies detected a band about 83 kDa and another about 41 kDa which were expected from the cDNA sequence. The fact that two bands were detected is consistent with the fact that two types of transcripts, one of about 4.4 and the other of about 2.5 kb, respectively, were detected in the Northern analysis. Interestingly, in HeLa cells, in which only the long band was detected by Northern analysis, only the 83 kDa band was detected by the Western analysis. On the other hand, in NIH3T3 cells, not only the band of about 85 kDa was detected by anti-Gros1 antibody, but also bands with the size of 61.5, 41, 34 and 32 kDa were detected. The bands of about 85 kDa and 61.5 kDa correspond to mouse Gros1-L and mouse Gros1-S, respectively, and the other bands correspond presumably to proteins cleaved or modified endogenously. In COS7 cells, 60, 40 and 34 kDa bands were detected. The cDNAs encoding either human Gros1-L or S were inserted into expression vectors and transfected into COS7 cells. As the expression vector, pCMV-SPORT Vector (GIBCO BRL) used in the screening of human testis library was used. As a result of Western blot analysis using anti-Gros1 antibody, either an 83 kDa band or 41 kDa band corresponding to the cDNA sequence was detected. In COS7 cells, in which this plasmid encoding GFP-Gros1 fusion protein described below was transfected, production of proteins corresponding to the sizes of Gros1-L or Gros1-S (115 kDa and 72 kDa, respectively) was confirmed by Western blot analysis after SDS-PAGE.

EXAMPLE 7 Localization of the Genes in the Cell

Two types of human Gros1 cDNA were amplified by PCR using sense (SEQ ID NO:13) and antisense (SEQ ID NO:14, 15) primers designed so as to comprise two types of open reading frames corresponding to human Gros1-L and S. “GFPC1/7-3.0”, which expresses the fusion protein of human Gros1-S, and “GFPC1/7-2.7”, which expresses the fusion protein of human Gros1-L, were prepared by inserting these genes to the C terminal region of GFP ORF in pEGFP-C1 (Clontech). With the usage of Tfx-50 (Promega), these plasmids encoding the GFP-Gros1 fusion protein and the controls plasmids encoding only the GFP were transfected into COS7 cells growing on the cover glass. The cells were fixed with 4% formaldehyde, 24 hours after the transfection, and were washed three times with PBS.

The cells were observed with an epifluorescence Olympus BH-2 microscope. As a result, the two types of proteins fused with different types of Gros1 full-length sequences were both localized in the cytoplasm (FIGS. 7 and 8).

EXAMPLE 8 Proliferation Repressing Activity

The Gros1 mutant cDNA/pBluescript encoding only the 369 amino acids at the N-terminus of mouse Gros1-L isolated by screening was cleaved with EcoRI, and ligated in the same manner as in Example 2, with SRa expression vector (Mol. Cell. Biol., 8:466-472, 1988), and treated with the restriction enzyme EcoRI. As a result, two clones, in sense and antisense directions, respectively, were obtained. To isolate a gene encoding the full-length mouse Gros1, EST clone AA49892A, which showed homology with mouse Gros1, was purchased from Genome System. The EST clone and Gros1 cDNA/pBluescript were both treated with restriction enzymes ScaI and NotI, and the gene fragments were ligated in the same manner as in Example 2 to obtain the mouse Gros1-L gene. This Gros1-L gene fragment was further treated with restriction enzymes at the EcoRI-NotI site and ligated to the SRα expression vector treated with restriction enzymes at the same site in the same manner as in Example 2. As a result, the SRa/Gros 1-L sense clone which expresses mouse Gros1-L was isolated.

Six G418 resistance clones were obtained by introducing the above vectors into NIH3T3 cells and expression of Gros1 in each vector was confirmed by Northern blot analysis (FIG. 9). Among these, a clone in sense direction with especially high expression and a clone in antisense direction in which endogenous Gros1 transcript was rarely detected by Northern analysis were subjected to the colony forming activity test.

500 cells of each clone were spread on a 10 cm dish, and cultured for 2 weeks by replacing the medium once every three days. The cells were fixed with PBS containing 4% formaldehyde and stained with methylene blue to count the number of colonies. The experiments were done in triplicate.

As a result, whereas colony formation was extremely delayed in clones transfected with Gros1-L in the sense direction, the colony formation in clones transfected with Gros1-L in the antisense direction was as about 5 times higher than the control (FIG. 10, Table 1). In Gros1-mutant in the sense direction, no decrease of colony formation was observed (“defective colonies” in Table 1). From results above, Gros1 protein was shown to have an activity to repress proliferation.

TABLE 1 Number of colonies Cloned Cell Dish 1 Dish 2 Control colonies Control 702 197 150 Control 733 223 106 Sense colonies NIH3T3/7-7m3 S2 38 42 NIH3T3/7-7m3 S4 23 40 NIH3T3/7-7m3 S5 40 60 NIH3T3/7-7m3 S6 33 9 NIH3T3/7-7m3 S10 39 16 Antisense colonies #723 181 186 #AS1 190 169 #AS2 276 336 #AS3 398 341 #AS10 209 187 #AS12 233 254 Defective colonies #715 201 215 #719 179 193 #774 156 113 #784 103 117 #738 97 80

INDUSTRIAL APPLICABILITY

The presence of non-random mutations on human chromosome 1p in many malignant tumors was proposed by cytogenetic and molecular biological approaches. These facts suggest that one or more gene mutations on chromosome 1p are important for malignant tumors. As the human Gros1 gene of the present invention is present on the chromosome 1p region and has the activity to suppress tumors, this gene may be a causative gene for these diseases. Therefore, the proteins or genes of the present invention, as well as a compound which promotes the activity of the proteins of the present invention can be used as useful tools for purifying and cloning novel factors involved in cell proliferation, and furthermore, can be used for developing pharmaceuticals for treating or preventing various tumors. 

What is claimed is:
 1. A substantially purified polypeptide comprising the amino acid sequence of SEQ ID NO:2.
 2. A method for identifying a compound that binds to the polypeptide of claim 1, the method comprising: (a) contacting the polypeptide of claim 1 with a test compound, (b) determining whether the test compound binds to the polypeptide, and (c) selecting the test compound if it binds to the polypeptide.
 3. A substantially purified polypeptide encoded by the nucleotide sequence of SEQ ID NO:1.
 4. A method for identifying a compound that binds to the polypeptide of claim 3, the method comprising (a) contacting the polypeptide of claim 3 with a test compound, (b) determining whether the test compound binds to the polypeptide, and (c) selecting the test compound if it binds to the polypeptide. 